Hi Team,
We would like to ask your help regarding our customer's inquiry below.
My issue with the TPS23882 POE controller is simple: power is removed from a specified port via register 0x19 "power enable", but in about 2-3 seconds, power is restored automatically.
The operating mode register (0x12) = 0xFF suggesting it is in AUTO mode.
The control plane in my system is based on a Microchip SAME70 processor. Upon system startup, the control plane will:
- setup clocking over the I2C interface
- configure the TPS23882 = "configuration B" mode with "general mask" 17h = 0xA0 for word read/write access
- read (byte) "device ID" 43h = 0x33
- read (byte) "manufacturer ID" 1B = 0x55
The interface to the TPS device is seemingly correctly setup.
For power enable/disable, I chose port 1 for testing as a convenience. I number the steps below to clarify any response you may have.
1. all reads and writes w.r.t. the TPS device over I2C can be either 1-byte/8bits basis, or by 16-bits/1-word basis
2. when read/write are by 1-byte: bit settings reference ports 4,3,2,1 as per the TSP23882 data sheet
3. when read/write are by 1-word: bit settings reference:
- ports 8,7,6,5 are in the most significant byte of the word
- ports 4,3,2,1 are in the least-significant byte of the word
Testing:
4. there are no devices connected to any port
5. command 10h read "power status". Value = 0x0000 = power not good/channel is OFF on all channels
6. connect a POE device on port 1, wait a bit
7. command 10h read. Value = 0x0011 = power is good/channel is ON (both bits PG1 and PE1 = 1)
8. command 19h "power enable": write 0x0010 to write 1 to POFF1 bit. Result: power over port 1 remains.
9. From page 63 of the TSP23882 data sheet: "Writing a “1” at POFFn and PWONn on same Channel during the same write operation turns the Channel off", so:
2. when read/write are by 1-byte: bit settings reference ports 4,3,2,1 as per the TSP23882 data sheet
3. when read/write are by 1-word: bit settings reference:
- ports 8,7,6,5 are in the most significant byte of the word
- ports 4,3,2,1 are in the least-significant byte of the word
Testing:
4. there are no devices connected to any port
5. command 10h read "power status". Value = 0x0000 = power not good/channel is OFF on all channels
6. connect a POE device on port 1, wait a bit
7. command 10h read. Value = 0x0011 = power is good/channel is ON (both bits PG1 and PE1 = 1)
8. command 19h "power enable": write 0x0010 to write 1 to POFF1 bit. Result: power over port 1 remains.
9. From page 63 of the TSP23882 data sheet: "Writing a “1” at POFFn and PWONn on same Channel during the same write operation turns the Channel off", so:
command 19h: write 0x0011 to write 1 to POFF1 and PWON1 bits. Result: power over port 1 remains.
10. If the byte-ordering in items 8/9 above were inadvertently reversed:
11. command 19h: write 0x1000 to write 1 to POFF1 bit. Result: power over port 1 remains.
12. command 19h: write 0x1100 to write 1 to POFF1 and PWON1 bits. Result: power over port 1 remains.
13. If command 19h is written as a single-byte only:
14. command 19h: write 0x10 (1 byte) to write 1 to POFF1 bit. Result: power over port 1 remains.
15. command 19h: write 0x11 (1 byte) to write 1 to POFF1 and PWON1 bits. Result: power over port 1 remains.
16. Assuming that the Operating Mode register must be set to semi-auto:
17. command 12h: read 1 byte: value = 0xFF indicating that channels 4,3,2,1 = Auto mode
18. command 12h: write 0x02 (1 byte) to set C1M1/C1M0 bits = 10 = port 1 in semi-auto mode
19. command 12h: read back 1 byte: value = 0xFF ... presumably, channels 4,3,2,1 are still in AUTO mode
20. repeat the writes with command 19h to disable power on port. Power is not disabled.
10. If the byte-ordering in items 8/9 above were inadvertently reversed:
11. command 19h: write 0x1000 to write 1 to POFF1 bit. Result: power over port 1 remains.
12. command 19h: write 0x1100 to write 1 to POFF1 and PWON1 bits. Result: power over port 1 remains.
13. If command 19h is written as a single-byte only:
14. command 19h: write 0x10 (1 byte) to write 1 to POFF1 bit. Result: power over port 1 remains.
15. command 19h: write 0x11 (1 byte) to write 1 to POFF1 and PWON1 bits. Result: power over port 1 remains.
16. Assuming that the Operating Mode register must be set to semi-auto:
17. command 12h: read 1 byte: value = 0xFF indicating that channels 4,3,2,1 = Auto mode
18. command 12h: write 0x02 (1 byte) to set C1M1/C1M0 bits = 10 = port 1 in semi-auto mode
19. command 12h: read back 1 byte: value = 0xFF ... presumably, channels 4,3,2,1 are still in AUTO mode
20. repeat the writes with command 19h to disable power on port. Power is not disabled.
21. command 12h: write 0xAA (1 byte) to set 4 pairs of CxM1/CxM0 bits = 10 = ports 4,3,2,1 in semi-auto mode
22. command 12h: read back 1 byte: value = 0xFF ... presumably, the write did not take effect
22. command 12h: read back 1 byte: value = 0xFF ... presumably, the write did not take effect
23. I downloaded the slvc790.zip file from the TI site and extracted the sample C code.
24. I will examine the C sample code to see if I can glean better insight into accessing the TSP23882 POE device.
25. Is there a preferred IDE to view the slvc790 code set?
Regards,
Danilo
